The "Save As" and "Open" buttons still used an old implementation that
assumed you were talking about files only in the "./maps" folder instead
of loading them from the user's levels and doodads folders.
Now all of the menu buttons in Edit Mode intelligently open files the
same as the `edit <filename>` command from the dev console. You can omit
the file extension and it will attempt to load a Level before a Doodad
to find the first named file, or provide the full extension to be
specific.
* Scenes can insert custom key/value labels to the debug overlay and
track string variables in real time
* Added ability to unthrottle FPS in main loop
